The "Confessions of a Shopaholic" star and her husband, Sacha Baron Cohen, were rumored to have been expecting a second child earlier this year. The secretive couple refused to confirm the news and reports about the birth only surfaced when they were

spotted pushing a stroller around London in September.

Fisher has finally spoken out about her pregnancy, admitting she kept the news quiet during the filming of new movie with Simon Pegg and Andy Serkis, who play infamous British grave robbers.

She says, "That was difficult because I was pregnant during the making of the movie, so I didn't really squeeze into it (the corset). I used to pretend I was wearing a corset and then not wear it, just wear a push up bra -- don't tell the director that."

Pegg confirms he had no idea his co-star was pregnant until he saw her sporting a full baby bump months after

the shoot wrapped.

He adds, "I didn't know what was going on. She didn't look pregnant until the last minute. I saw her a couple of months later and she was like a balloon. None of us knew, not even John knew. She hid it well."

Fisher has a daughter, Olive, with Cohen, but they have yet to reveal the gender or the name of their new baby.